What does it mean?
P1793 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: A/T Manifold Absolute Pressure Sensor Circuit Malfunction .
Symptoms
- MIL (check engine lamp) is on, usually with engine fuel trim or performance codes
- Shift points are clearly wrong and shifts feel either harsh or slurred
- Poor acceleration, hesitation and a lack of power under load
- Rough idle, and a rich fuel smell or black smoke from the exhaust
- Fuel consumption rises noticeably
- Transmission may drop into limp mode
Likely causes
- MAP sensor failed, drifted or contaminated by fuel and carbon at its port
- Cracked, collapsed or disconnected vacuum hose feeding the sensor
- Blocked sensor port or passage in the intake manifold
- Corroded connector, or an open or shorted signal, reference or ground wire
- Large intake vacuum leak, so the actual manifold pressure genuinely does not match engine load
- Missing or corrupted MAP message reaching the transmission module
- Control module input circuit fault
How to fix it
- Inspect the vacuum hose and the manifold port for cracks, blockage and oil contamination
- With the ignition on and the engine off, compare the MAP reading against local atmospheric pressure; they should agree
- Compare the MAP reading at idle against a vacuum gauge fitted to the manifold
- Back-probe the signal wire and verify it changes smoothly as engine load changes
- Check the 5 V reference and ground at the sensor connector, and inspect for corrosion
- Test for intake leaks, then replace the sensor once the hose, port and wiring are proven good